Capacitated Dynamic Lot-sizing for Remanufacturing Systems with Parallel Reprocessing Workstations

Abstract

This study considers a dynamic lot-sizing problem for remanufacturing systems that consists of a single disassembly, parallel reprocessing and a single reassembly workstations. The problem is to determine the disassembly, reprocessing and reassembly lot-sizes that satisfy the remanufactured product demands while satisfying the capacity of each facility over a planning horizon for the objective of minimizing the sum of setup, operation and inventory holding costs. A mixed integer programming model is developed to represent the problem mathematically. Then, three heuristics are proposed that fixes a portion of binary variables and solves the resulting problems iteratively. Computational experiments were done on various test instances and the test results are reported. Index Terms-remanufacturing, lot-sizing, fix-and-optimize. I. INTRODUCTION Remanufacturing is defined as recycling by manufacturing new products from end-of-use/life products, i.e. reprocessing end-of-use/life products in such a way that their qualities are as good as new in the aspects of appearance, reliability and performance. As explained in Steinhilper [1], remanufacturing is different from repair in that it is an industrialized process, not a simple mechanical work, with an overall restoration to likely new conditions after products are disassembled completely. A typical remanufacturing system consists of three dependent processes, i.e. disassembly, reprocessing and reassembly. An end-of-use/life product is separated into its components in the disassembly process, and then, the usable ones are cleaned, reconditioned and tested in the reprocessing process. Finally, in the reassembly process, reprocessed and new components, if required, are assembled into the remanufactured product fully equivalent in performance and ready for use by customers. As various decision problems in remanufacturing systems, we focus on the planning problem that determines the lot-sizes that satisfy the demands of remanufactured products, i.e. how much and when to disassemble end-of-life products, reprocess their components and reassemble remanufactured products. See Guide [2] for the importance of planning in remanufacturing systems.